Projector, projected image adjustment method, and program for projecting an image while correcting the shape of the image to project an image at a desired aspect ratio

ABSTRACT

A projector includes a projection section which projects a calibration image onto a projection target through a projection panel, a shape determination section which determines a shape of the projection target, a correction target area setting section which sets a correction target area, an aspect ratio calculation section which calculates an aspect ratio of the correction target area, a determination section which determines whether or not a value which indicates a difference between the aspect ratio of the correction target area and a reference aspect ratio satisfies a set condition, and an image generation section which generates an image having the shape of the correction target area on the projection panel when the set condition is satisfied, and generates an image having the reference aspect ratio on the projection panel when the set condition is not satisfied.

This is a Continuation of application Ser. No. 12/068,659 filed Feb. 8,2008, which claims the benefit of Japanese Patent Application No.2007-044241, filed on Feb. 23, 2007, which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a projector, a projected imageadjustment method, and a program for projecting an image whilecorrecting the shape of the image.

When a projector projects an image onto a screen or the like, theprojected image may be distorted. As a method of correcting suchdistortion of an image, JP-A-2005-286572 proposes a method in which theuser adjusts the position of a projected image so that the four cornersof the projected image coincide with the four corners of a projectiontarget such as a screen, the aspect ratio of the projection target iscalculated based on position adjustment information, and positioncorrection information is generated based on the aspect ratio so thatthe projected image has a predetermined aspect ratio, for example.

However, when a projector projects an image with an aspect ratio of 4:3when the aspect ratio of the projection target is about 4:3.1, the imageis not projected at the upper end and the lower end of the projectiontarget, whereby the user may have a wrong impression. A non-display areaalso occurs on the projection target when a sensed image is affected byan error due to optical distortion, noise, resolution limits of asensing section, and the like, whereby the user may also have a wrongimpression.

SUMMARY

According to a first aspect of the invention, there is provided aprojector comprising:

a projection section which projects a calibration image onto aprojection target through a projection panel;

a shape determination section which determines at least part of a shapeof the projection target based on sensing information from a sensingsection in a state in which the calibration image is projected onto theprojection target or operation information from an operation section ina state in which the calibration image is projected onto the projectiontarget;

a correction target area setting section which sets a correction targetarea, the correction target area being an area along the shapedetermined by the shape determination section and being an area on theprojection panel;

an aspect ratio calculation section which calculates an aspect ratio ofthe correction target area;

a determination section which determines whether or not a value whichindicates a difference between the aspect ratio of the correction targetarea and a reference aspect ratio satisfies a set condition; and

an image generation section which generates an image having the shape ofthe correction target area on the projection panel when the setcondition is satisfied, and generates an image having the referenceaspect ratio on the projection panel when the set condition is notsatisfied.

According to a second aspect of the invention, there is provided aprojected image adjustment method using a projector, the methodcomprising causing the projector to:

project a calibration image onto a projection target through aprojection panel;

determine a shape of at least part of the projection target based onsensing information from a sensing section in a state in which thecalibration image is projected onto the projection target or operationinformation from an operation section in a state in which thecalibration image is projected onto the projection target;

set a correction target area, the correction target area being an areaalong the determined shape and being an area on the projection panel;

calculate an aspect ratio of the correction target area;

determine whether or not a value which indicates a difference betweenthe aspect ratio of the correction target area and a reference aspectratio satisfies a set condition;

generate an image having the shape of the correction target area on theprojection panel when the set condition is satisfied, and generate animage having the reference aspect ratio on the projection panel when theset condition is not satisfied; and

project the image generated on the projection panel.

According to a third aspect of the invention, there is provided aprogram readable by a computer included in a projector including aprojection section, the program causing the computer to function as:

a projection control section which causes a projection section toproject a calibration image onto a projection target through aprojection panel;

a shape determination section which determines at least part of a shapeof the projection target based on sensing information from a sensingsection in a state in which the calibration image is projected onto theprojection target or operation information from an operation section ina state in which the calibration image is projected onto the projectiontarget;

a correction target area setting section which sets a correction targetarea, the correction target area being an area along the shapedetermined by the shape determination section and being an area on theprojection panel;

an aspect ratio calculation section which calculates an aspect ratio ofthe correction target area;

a determination section which determines whether or not a value whichindicates a difference between the aspect ratio of the correction targetarea and a reference aspect ratio satisfies a set condition; and

an image generation section which generates an image having the shape ofthe correction target area on the projection panel when the setcondition is satisfied, and generates an image having the referenceaspect ratio on the projection panel when the set condition is notsatisfied.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagram showing a projected image according to related art.

FIG. 2 is a diagram showing a roll angle of a projector.

FIG. 3 is a diagram showing a projected image after distortioncorrection according to related art.

FIG. 4 is a functional block diagram of a projector according to a firstembodiment of the invention.

FIG. 5 is a flowchart showing a projection process according to thefirst embodiment of the invention.

FIG. 6A is a diagram showing a solid white calibration image, FIG. 6B isa diagram showing a center-white calibration image, and FIG. 6C is adiagram showing a solid black calibration image.

FIG. 7A is a diagram showing a sensed image of a solid white calibrationimage, FIG. 7B is a diagram showing a sensed image of a center-whitecalibration image, and FIG. 7C is a diagram showing a sensed image of asolid black calibration image.

FIG. 8 is a diagram showing an example of a screen in a sensed imageafter correction.

FIG. 9 is a flowchart showing a correction target area setting processaccording to the first embodiment of the invention.

FIG. 10 is a diagram schematically showing a vertical vanishing pointand a horizontal vanishing point.

FIG. 11 is a flowchart showing an aspect ratio correction processaccording to the first embodiment of the invention.

FIG. 12 is a functional block diagram of a projector according to asecond embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

The invention may provide a projector, a projected image adjustmentmethod, and a program capable of projecting an image at an aspect ratiocorresponding to the situation.

According to one embodiment of the invention, there is provided aprojector comprising:

a projection section which projects a calibration image onto aprojection target through a projection panel;

a shape determination section which determines at least part of a shapeof the projection target based on sensing information from a sensingsection in a state in which the calibration image is projected onto theprojection target or operation information from an operation section ina state in which the calibration image is projected onto the projectiontarget;

a correction target area setting section which sets a correction targetarea, the correction target area being an area along the shapedetermined by the shape determination section and being an area on theprojection panel;

an aspect ratio calculation section which calculates an aspect ratio ofthe correction target area;

a determination section which determines whether or not a value whichindicates a difference between the aspect ratio of the correction targetarea and a reference aspect ratio satisfies a set condition; and

an image generation section which generates an image having the shape ofthe correction target area on the projection panel when the setcondition is satisfied, and generates an image having the referenceaspect ratio on the projection panel when the set condition is notsatisfied.

According to one embodiment of the invention, there is provided aprojected image adjustment method using a projector, the methodcomprising causing the projector to:

project a calibration image onto a projection target through aprojection panel;

determine a shape of at least part of the projection target based onsensing information from a sensing section in a state in which thecalibration image is projected onto the projection target or operationinformation from an operation section in a state in which thecalibration image is projected onto the projection target;

set a correction target area, the correction target area being an areaalong the determined shape and being an area on the projection panel;

calculate an aspect ratio of the correction target area;

determine whether or not a value which indicates a difference betweenthe aspect ratio of the correction target area and a reference aspectratio satisfies a set condition;

generate an image having the shape of the correction target area on theprojection panel when the set condition is satisfied, and generate animage having the reference aspect ratio on the projection panel when theset condition is not satisfied; and

project the image generated on the projection panel.

According to one embodiment of the invention, there is provided aprogram readable by a computer included in a projector including aprojection section, the program causing the computer to function as:

a projection control section which causes a projection section toproject a calibration image onto a projection target through aprojection panel;

a shape determination section which determines at least part of a shapeof the projection target based on sensing information from a sensingsection in a state in which the calibration image is projected onto theprojection target or operation information from an operation section ina state in which the calibration image is projected onto the projectiontarget;

a correction target area setting section which sets a correction targetarea, the correction target area being an area along the shapedetermined by the shape determination section and being an area on theprojection panel;

an aspect ratio calculation section which calculates an aspect ratio ofthe correction target area;

a determination section which determines whether or not a value whichindicates a difference between the aspect ratio of the correction targetarea and a reference aspect ratio satisfies a set condition; and

an image generation section which generates an image having the shape ofthe correction target area on the projection panel when the setcondition is satisfied, and generates an image having the referenceaspect ratio on the projection panel when the set condition is notsatisfied.

According to one embodiment of the invention, there is provided aninformation storage medium storing the program which is readable by acomputer included in a projector having a projection section.

According to the above embodiment, the projector can project an image atan aspect ratio corresponding to the situation by determining the valuewhich indicates the difference between the aspect ratio of thecorrection target area and the reference aspect ratio satisfies the setcondition, and projecting an image at an aspect ratio corresponding tothe determination result.

The sensing section may sense an area including at least part of thecalibration image projected by the projection section and at least partof the projection target to generate the sensing information whichindicates a sensed image; and

the shape determination section may determine the shape of at least partof the projection target included in the sensed image based on thesensing information.

The projector may sense an area including at least part of thecalibration image projected by the projection section and at least partof the projection target to generate sensing information which indicatesa sensed image, and determine at least part of the shape of theprojection target included in the sensed image based on the sensinginformation.

Since the projector can thus determine the shape of at least part of theprojection target based on the sensing information, the projector canproject an image at a desired aspect ratio without inputting operationinformation.

When the shape of the entire projection target has not been determinedby the shape determination section, the correction target area settingsection may determine coordinate values of a vertical vanishing pointand a horizontal vanishing point formed by sides of the projectiontarget in a coordinate system of the projection panel based on thesensing information, and supplement a portion of the projection targetwhich has not determined by the shape determination section based on thecoordinate values.

When the shape of the entire projection target has not been determined,the projector may determine coordinate values of a vertical vanishingpoint and a horizontal vanishing point formed by sides of the projectiontarget in a coordinate system of the projection panel based on thesensing information, and supplement a portion of the projection targetwhich has not determined based on the coordinate values.

Since the projector can thus supplement the undetermined portion of theprojection target even if the entire projection target is not includedin the sensed image, the projector can more generally project an imageat an aspect ratio corresponding to the situation.

The determination section may determine whether or not the set conditionis satisfied by determining whether or not the value which indicates thedifference between the aspect ratio of the correction target area andthe reference aspect ratio is within a predetermined range.

The projector may determine whether or not the set condition issatisfied by determining whether or not the value which indicates thedifference between the aspect ratio of the correction target area andthe reference aspect ratio is within a predetermined range.

Since the projector can thus absorb a measurement error and the like bydetermining the difference in aspect ratio utilizing the range, asituation in which a non-display area occurs on the projection targetcan be prevented.

When the shape of the entire projection target has not been determinedby the shape determination section, the determination section may reducethe predetermined range as compared with the case where the shape of theentire projection target has been determined by the shape determinationsection.

When the entire shape of the projection target has not been determined,the projector may reduce the predetermined range as compared with thecase where the entire shape of the projection target has beendetermined.

The projector thus can more strictly deal with the case where distortionof an image occurs to a large extent, for example, whereby a situationin which an image having a wrong shape is projected can be prevented.

The correction target area setting section may set an area larger thanthe shape determined by the shape determination section by at least onepixel as the correction target area.

The projector may set an area larger than the determined shape by atleast one pixel as the correction target area.

Since the projector thus sets an area larger than the determined shapeby at least one pixel as the correction target area, a situation inwhich a non-display area occurs on the projection target can beprevented.

The invention is described below with reference to the drawings takingthe case of applying the invention to a projector as an example. Notethat the embodiments described hereunder do not in any way limit thescope of the invention defined by the claims laid out herein. Note alsothat not all of the elements of the embodiments should be taken asessential requirements to the invention.

Problems of Related Art

FIG. 1 is a diagram showing a projected image 12 according to relatedart. A related-art projector projects an image with an aspect ratio of4:3 based on the setting even if the aspect ratio of a screen 10 (onetype of projection target) is about 4:3.1. Therefore, the image is notprojected at the upper end and the lower end of the screen 10, as shownin FIG. 1, whereby the user may have a wrong impression. A related-artprojector corrects distortion of an image based on a sensed image. Whenthe sensed image is affected by an error due to optical distortion,noise, resolution limits of a sensing section, and the like, anon-display area occurs on the screen 10, whereby the user may also havea wrong impression.

FIG. 2 is a diagram showing the roll angle of a projector 20. Therelated-art projector 20 corrects distortion of an image depending onthe projection angle in the vertical direction (pitch angle) and theprojection angle in the horizontal direction (yaw angle). Since theprojector 20 does not utilize the rotation angle (roll angle) of theprojector 20 with respect to the optical axis of projection light,distortion of an image cannot be accurately corrected when a table orthe like on which the projector 20 is placed inclines.

FIG. 3 is a diagram showing the projected image 12 after distortioncorrection according to related art. The related-art projector 20performs a number of calculations using the coordinate values of thesensing area (e.g., CCD panel) of the sensing section (e.g., CCDsensor). Therefore, even if the position of the sensing section providedin the projector 20 differs from the original position to only a smallextent, the projected image 12 after distortion correction according torelated art is distorted as shown in FIG. 3.

First Embodiment

In order to solve these problems, a projector according to thisembodiment has a function of projecting an image at an aspect ratiocorresponding to the situation by determining a value which indicatesthe difference between the aspect ratio of a correction target area anda reference aspect ratio satisfies a set condition, and projecting animage at an aspect ratio corresponding to the determination result. Theprojector according to this embodiment has a function of correctingdistortion of an image using the roll angle. The projector according tothis embodiment also has a function of performing calculations relatingto the coordinate value of an image using the coordinate system of aprojection panel.

Functional blocks of a projector 100 having these functions aredescribed below. FIG. 4 is a functional block diagram of the projector100 according to a first embodiment. The projector 100 is configured toinclude a sensing section 110 which senses a calibration image projectedonto a screen 10 to generate sensing information which indicates thesensed image, a storage section 120 which stores various types of data,and a shape determination section 130 which determines the shape of atleast part of the screen 10 based on the sensing information.

The storage section 120 stores image information 122 for generating animage, sensing information 124 from the sensing section 110, andreference data 126 which indicates a reference aspect ratio, adetermination reference value, and the like, for example.

The projector 100 is configured to include a correction target areasetting section 140 which sets a correction target area, an imagegeneration section 150 which generates an image in the correction targetarea of a liquid crystal panel which is one type of projection panel, aprojection section 190 which projects the image, an aspect ratiocalculation section 170 which calculates the aspect ratio of thecorrection target area, a determination section 172 which makes variousdeterminations, and a vertical projection angle determination section180 which determines the vertical projection angle of the projector 100.

The correction target area setting section 140 is configured to includea correction target position information generation section 142 whichgenerates correction target position information based on theinformation from the shape determination section 130, a coordinatetransformation section 144 which transforms the coordinate value of thesensing area into the coordinate value of the liquid crystal panel, andan area setting section 146 which sets the correction target area basedon the coordinate value.

As hardware of the projector 100 which implements the function of eachsection, the following hardware may be used, for example. For example, aCCD sensor or the like may be used as the sensing section 110. A RAM, anHDD, or the like may be used as the storage section 120. A CPU or thelike may be used as the shape determination section 130, the correctiontarget area setting section 140, the aspect ratio calculation section170, and the determination section 172. An image processing circuit, aliquid crystal driver circuit, or the like may be used as the imagegeneration section 150. An angle sensor or the like may be used as thevertical projection angle determination section 180. A liquid crystalpanel, a lamp, a projection lens, and the like may be used as theprojection section 190.

The function of each section may be implemented by causing the projector100 to read a program which implements the function of each section froman information storage medium 200 which stores the program. As theinformation storage medium 200, a CD-ROM, a DVD-ROM, a ROM, a RAM, anHDD, or the like may be applied. The program reading method may be acontact method or a noncontact method.

A projection process using each section is as follows. FIG. 5 is aflowchart showing the projection process according to the firstembodiment. For example, the projector 100 corrects distortion of animage when the projector 100 has been activated, when the user hasdirected correction, or the like. When the projector 100 correctsdistortion of an image, the image generation section 150 generates acalibration image based on the image information 122, and the projectionsection 190 projects the calibration image onto the screen 10 (step S1).

The sensing section 110 senses the calibration image projected onto thescreen 10 to generate the sensing information 124, and stores thesensing information 124 in the storage section 120 (step S2). In thisembodiment, the projector 100 projects and senses three types ofcalibration images.

FIG. 6A is a diagram showing a solid white calibration image 300, FIG.6B is a diagram showing a center-white calibration image 301, and FIG.6C is a diagram showing a solid black calibration image 302. Theprojector 20 projects the solid white (i.e., the entire image is white)calibration image 300, and senses the projected calibration image 300 byautomatic exposure.

The projector 100 then projects the calibration image 301 in which acenter area having a shape proportional to that of the entire image(e.g., an area which is 1/9th of the entire image and is positioned atthe center of the image) is white and an area other than the center areais black, and senses the projected calibration image 301 at an exposuredetermined by automatic exposure when sensing the calibration image 300.The projector 20 then projects the solid black (i.e., the entire imageis black) calibration image 302, and senses the projected calibrationimage 302 at an exposure determined by automatic exposure when sensingthe calibration image 300.

FIG. 7A is a diagram showing a sensed image 400 of the solid whitecalibration image 300, FIG. 7B is a diagram showing a sensed image 401of the center-white calibration image 301, and FIG. 7C is a diagramshowing a sensed image 402 of the solid black calibration image 302.

For example, even if the calibration image 300 is partially positionedoutside the screen 10, as shown in FIG. 7A, the center area of thecalibration image 301 is projected onto the screen 10, as shown in FIG.7B. Therefore, the projector 100 can determine the luminance value,shape, and the like of the solid white image on the screen 10. Note thatthe three types of calibration images 300 to 302 may be sensed in anarbitrary order.

The shape determination section 130 determines whether or not thesensing section 110 has sensed the three types of calibration images 300to 302 (step S3). When the shape determination section 130 hasdetermined that the sensing section 110 has sensed the three types ofcalibration images 300 to 302, the shape determination section 130generates projection target position information which indicates theposition of the screen 10 in the sensing area based on the sensinginformation 124 (step S4). Specifically, the shape determination section130 generates a differential image between the sensed image 400 and thesensed image 402, determines the boundary line between the screen 10 andthe background in the sensing area by performing edge detection and thelike on the differential image, and generates the projection targetposition information relating to the position of the boundary line. Thedifferential image is used in order to eliminate the effects of noisewhich occurs when light from a fluorescent lamp and the like isreflected in the sensed image 400 and the like.

The correction target position information generation section 142generates correction target position information based on the projectiontarget position information from the shape determination section 130(step S5). FIG. 8 is a diagram showing of an example of the screen 10 inthe sensed image 403 after correction. For example, the correctiontarget position information generation section 142 sets an area ABCD(area indicated by a broken line in FIG. 8) generated by enlarging thescreen 10 in the sensed image 403 by one pixel, and generates thecorrection target position information relating to the position of thearea ABCD (e.g., information which indicates the coordinate values ofthe four corners of the area ABCD in the sensing area).

The coordinate transformation section 144 transforms the coordinatevalues of the area ABCD in the sensing area into coordinate values onthe liquid crystal panel based on the correction target positioninformation from the correction target position information generationsection 142 (step S6). The coordinate values are transformed byprojective transformation and the like.

The area setting section 146 sets the correction target area based onthe coordinate values after transformation by the coordinate conversionsection 144 (step S7). The correction target area setting is describedbelow in detail. FIG. 9 is a flowchart showing the correction targetarea setting process according to the first embodiment.

The area setting section 146 determines whether or not the shapedetermination section 130 has detected four sides of the screen 10 inthe differential image (step S11). When the area setting section 146 hasdetermined that the shape determination section 130 has not detectedfour sides of the screen 10 in the differential image, the area settingsection 146 determines whether or not the shape determination section130 has detected three sides of the screen 10 (step S12).

FIG. 10 is a diagram schematically showing a vertical vanishing point Vand a horizontal vanishing point H. In the example shown in FIG. 10, theshape determination section 130 has detected three sides (upper side,lower side, and left side) of the screen 10. When the shapedetermination section 130 has detected three sides of the screen 10, thearea setting section 146 utilizes the vertical or horizontal vanishingpoint to determine the other vanishing point (step S13).

In the example shown in FIG. 10, the area setting section 146 sets avirtual projection plane 14 in a plane in which Z=1, and calculates thecoordinate value of the horizontal vanishing point H at which theextensions of the upper side and the lower side of the screen 10intersect.

The vertical vanishing point V is positioned on the extension of theleft side, and an angle HOV formed by each vanishing point and theorigin O is 90 degrees. The area setting section 146 calculates thecoordinate value of the vertical vanishing point V at which theextensions of the left side and the right side of the screen 10intersect utilizing these properties.

When the shape determination section 130 has not detected three sides ofthe screen 10, the area setting section 146 determines whether or notthe shape determination section 130 has detected a vertical side (leftside or right side) and a horizontal side (upper side or lower side) ofthe screen 10 (step S14). When the shape determination section 130 hasdetected the vertical side and the horizontal side of the screen 10, thearea setting section 146 determines each vanishing point based onequations in which the vertical projection angle, the horizontalprojection angle, and the roll angle are variables (step S15).

For example, when the vertical projection angle is referred to as θ, thehorizontal projection angle is referred to as φ, and the roll angle isreferred to as Ψ, the coordinate value (X, Y) of each vanishing point inthe virtual projection plane 14 is expressed as follows.

$\begin{matrix}{{{Vertical}\mspace{14mu}{Vanishing}\mspace{14mu}{Point}\mspace{14mu} V} = \left( {\frac{\sin\;{\psi cos\phi}}{{\sin\;{\psi sin\phi cos}\;\theta} + {\cos\;{\psi sin}\;\theta}},\frac{{{- \sin}\;{\psi sin\phi sin}\;\theta} + {\cos\;{\psi cos}\;\theta}}{{\sin\;{\psi sin\phi cos}\;\theta} + {\cos\;{\psi sin}\;\theta}}} \right)} & (1) \\{{{Horizontal}\mspace{14mu}{Vanishing}\mspace{14mu}{Point}\mspace{14mu} H} = \left( {\frac{\sin\;{\psi cos\phi}}{{\sin\;{\psi sin\phi cos}\;\theta} - {\sin\;{\psi sin}\;\theta}},\frac{{{- \cos}\;{\psi sin\phi sin}\;\theta} - {\sin\;{\psi cos}\;\theta}}{{\cos\;{\psi sin\phi cos}\;\theta} - {\sin\;{\psi sin}\;\theta}}} \right)} & (2)\end{matrix}$

The basis for these equations is described later.

The term “vertical projection angle” used herein refers to the relativevertical angle formed by the screen 10 and the optical axis ofprojection light emitted from the projection section 190, for example.The term “horizontal projection angle” used herein refers to therelative horizontal angle formed by the screen 10 and the optical axisof projection light emitted from the projection section 190, forexample. The vertical projection angle may be a value indicating thevertical slope of the projector 100 determined by the verticalprojection angle determination section 180.

The area setting section 146 can solve the above equations assimultaneous equations of φ and Ψ by substituting the value indicatingthe vertical slope of the projector 100 determined by the verticalprojection angle determination section 180 for θ to determine thevertical vanishing point and the horizontal vanishing point.

When the shape determination section 130 has not detected the verticalside and the horizontal side of the screen 10, the area setting section146 determines whether or not the shape determination section 130 hasdetected the upper side and the lower side of the screen 10 (step S16).When the shape determination section 130 has detected the upper side andthe lower side of the screen 10, the area setting section 146 determineseach vanishing point in the same manner as in the step S15 (step S17).Specifically, the area setting section 146 determines the horizontalvanishing point based on position information relating to the upper sideand the lower side. The area setting section 146 can solve the aboveequations as simultaneous equations of φ and Ψ by substituting the valueindicating the vertical slope of the projector 100 determined by thevertical projection angle determination section 180 for θ to determinethe vertical vanishing point.

When the shape determination section 130 has not detected the upper sideand the lower side of the screen 10, the area setting section 146determines whether or not the shape determination section 130 hasdetected the upper side or the lower side of the screen 10 (step S18).When the shape determination section 130 has detected the upper side orthe lower side of the screen 10, the area setting section 146 determineseach vanishing point using a method disclosed in JP-A-2006-60447 (stepS19).

When the above conditions are not satisfied, the image generationsection 150 generates an image which indicates that distortion of theimage cannot be corrected based on the image information 122, and theprojection section 190 projects the generated image (step S20). Theprojector 100 then finishes the distortion correction process.

When the area setting section 146 has determined each vanishing point isdetermined by the process in the step S13, S15, S17, or S19, the areasetting section 146 supplements the missing side of the correctiontarget area based on the known coordinate values of the screen 10 andthe coordinate value of each vanishing point (step S21).

The shape of the correction target area is determined by the aboveprocess. The area setting section 146 corrects the aspect ratio of thecorrection target area in a state in which the shape of the correctiontarget area has been determined (step S22). This aspect ratio correctionprocess is described below in detail. FIG. 11 is a flowchart showing theaspect ratio correction process according to the first embodiment.

The aspect ratio calculation section 170 calculates the aspect ratio ofthe correction target area determined by the area setting section 146(step S30). The term “aspect ratio” used herein refers to a valueobtained by dividing the length of the vertical side by the length ofthe horizontal side. For example, when the ratio of the length of thehorizontal side to the length of the vertical side is 4:3, the aspectratio is 0.75.

The determination section 172 determines whether or not the shapedetermination section 130 has detected the four sides of the screen 10(step S31). When the determination section 172 has determined that theshape determination section 130 has detected the four sides of thescreen 10, the determination section 172 sets a condition whereby thedifference between the aspect ratio of the correction target area andthe reference aspect ratio is 10% or less (step S32).

The term “reference aspect ratio” used herein refers to a desired aspectratio set by the manufacturer or the user of the projector 100, forexample. The reference aspect ratio is stored in the storage section 120as reference data 126. For example, when the reference aspect ratio is0.75, the above condition is satisfied when the aspect ratio of thecorrection target area is 0.675 or more and 0.825 or less.

When the determination section 172 has determined that the shapedetermination section 130 has not detected the four sides of the screen10, the determination section 172 sets a condition whereby thedifference between the aspect ratio of the correction target area andthe reference aspect ratio is 3% or less (step S32). For example, whenthe reference aspect ratio is 0.75, the above condition is satisfiedwhen the aspect ratio of the correction target area is 0.7275 or moreand 0.7725 or less.

The determination section 172 determines whether or not the aspect ratioof the correction target area calculated by the aspect ratio calculationsection 170 satisfies the set condition (step S34). When the aspectratio of the correction target does not satisfy the condition, thedetermination section 172 sets the correction target area so that theaspect ratio of the correction target area becomes equal to thereference aspect ratio (step S35).

The determination section 172 outputs information which indicates thecoordinate values of the four corners of the final correction targetarea on the liquid crystal panel to the image generation section 150.The image generation section 150 generates an image in the correctiontarget area on the liquid crystal panel based on the receivedinformation and the image information 122 (step S8). The projectionsection 190 projects the generated image (step S9).

As described above, the projector 100 according to this embodiment canproject an image at an aspect ratio corresponding to the situation bydetermining the value which indicates the difference between the aspectratio of the correction target area and the reference aspect ratiosatisfies the set condition, and projecting an image at an aspect ratiocorresponding to the determination result.

Since the projector 100 according to this embodiment can determine theshape of at least part of the screen 10 based on the sensinginformation, distortion of an image can be accurately corrected withoutinputting operation information, whereby the projector 100 can projectan image at the desired aspect ratio.

Since the projector 100 according to this embodiment can supplement anundetermined portion of the screen 10 even if the entire screen 10 isnot included in the sensed image, the projector 100 can more generallyproject an image at an aspect ratio corresponding to the situation.

Since the projector 100 according to this embodiment can absorb ameasurement error and the like by determining the difference in aspectratio utilizing the range, a situation in which a non-display areaoccurs on the screen 10 can be prevented.

When the shape determination section 130 has not detected the shape ofthe entire screen 10, the projector 100 according to this embodimentreduces the determination range as compared with the case where theshape determination section 130 has detected the shape of the entirescreen 10. Therefore, the projector 100 can more strictly deal with thecase where distortion of an image occurs to a large extent, for example,whereby a situation in which an image having a wrong shape is projectedcan be prevented.

The projector 100 according to this embodiment can prevent a situationin which a non-display area occurs on the screen 10 by setting an arealarger than the screen 10 by at least one pixel as the correction targetarea.

The projector 100 according to this embodiment can accurately correctdistortion of an image, even if the projector 100 inclines with respectto the optical axis of projection light or the sensing section 110 isincorrectly provided, by determining the coordinate values of thevertical vanishing point and the horizontal vanishing point formed bythe sides of the screen 10 in the coordinate system of the projectionpanel and supplementing a portion of the screen 10 which has not beendetermined by the shape determination section 130 based on thecoordinate values.

The projector 100 according to this embodiment can accurately correctdistortion of an image, even if the projector 100 inclines with respectto the optical axis of projection light, by performing calculationsusing the rotation angle of the projector 100 as a variable. Even if theprojector 100 according to this embodiment cannot perform calculationsusing the rotation angle of the projector 100 as a variable, theprojector 100 can correct distortion of an image by performingcalculations in which the rotation angle is 0 degrees.

The projector 100 according to this embodiment can appropriately correctdistortion of an image, even if the sensing section 110 is incorrectlyprovided, by setting the correction target area based on the coordinatevalues on the projection panel.

Calculation of Vanishing Point

The details of calculations of the vanishing points are given below. Ifthe pitch angle θ and the yaw angle φ are fixed, the correction shape isnot affected even if the screen 10 rotates in the roll direction.Therefore, the projector 100 is rotated in the order of the pitch angleθ, the yaw angle φ, and the roll angle Ψ.

A three-dimensional rotating matrix of the pitch angle θ, the yaw angleφ, and the roll angle Ψ is expressed as follows (the pitch angle θ isthe opposite direction (i.e., −θ)).

${{Rotating}\mspace{14mu}{Matrix}\mspace{14mu} R} = {\begin{pmatrix}{\cos\;\psi} & {{- \sin}\;\psi} & 0 \\{\sin\;\psi} & {\cos\;\psi} & 0 \\0 & 0 & 1\end{pmatrix}\begin{pmatrix}{\cos\;\phi} & 0 & {\sin\;\phi} \\0 & 1 & 0 \\{{- \sin}\;\phi} & 0 & {\cos\;\phi}\end{pmatrix}\begin{pmatrix}1 & 0 & 0 \\0 & {\cos\;\theta} & {\sin\;\theta} \\0 & {{- \sin}\;\theta} & {\cos\;\theta}\end{pmatrix}}$

Therefore, the following equation is obtained.

$R = \begin{pmatrix}{\cos\;{\psi cos\phi}} & {{{- \cos}\;{\psi sin\phi sin}\;\theta} - {\sin\;{\psi cos}\;\theta}} & {{\cos\;{\psi sin\phi cos}\;\theta} - {\sin\;{\psi sin}\;\theta}} \\{\sin\;{\psi cos}\;\phi} & {{{- \sin}\;{\psi sin\phi sin}\;\theta} + {\cos\;{\psi cos}\;\theta}} & {{\sin\;{\psi sin\phi cos}\;\theta} + {\cos\;{\psi sin}\;\theta}} \\{{- \sin}\;\phi} & {{- \cos}\;{\phi sin}\;\theta} & {\cos\;{\phi cos}\;\theta}\end{pmatrix}$

This matrix indicates rotation when the projector 100 is viewed from theoutside. The projector 100 rotates in the direction opposite to thismatrix when viewed from the projector 100. Therefore, a coordinatetransformation matrix which indicates rotation of the screen 10 viewedfrom the projector 100 is an inverse matrix of this matrix. Since arotating matrix is one type of orthogonal matrix, the inverse matrix maybe calculated by calculating the following transposed matrix.

${{Transposed}\mspace{14mu}{Matrix}\mspace{14mu} R^{\prime}} = \begin{pmatrix}{\cos\;{\psi cos\phi}} & {\sin\;{\psi cos}\;\phi} & {{- \sin}\;\phi} \\{{{- \cos}\;{\psi sin\phi sin}\;\theta} - {\sin\;{\psi cos}\;\theta}} & {{{- \sin}\;{\psi sin\phi sin}\;\theta} + {\cos\;{\psi cos}\;\theta}} & {{- \cos}\;{\phi sin}\;\theta} \\{{\cos\;{\psi sin\phi cos}\;\theta} - {\sin\;{\psi sin}\;\theta}} & {{\sin\;{\psi sin\phi cos}\;\theta} + {\cos\;{\psi sin}\;\theta}} & {\cos\;{\phi cos}\;\theta}\end{pmatrix}$

The vanishing point can be calculated by rotating the point at infinity[1:0:0] in the horizontal direction and the point at infinity [0:1:0] inthe vertical direction before rotation using the transposed matrix R′.Specifically, the vertical vanishing point and the horizontal vanishingpoint perpendicularly intersect in a three-dimensional space. The normalto the screen 10 can be calculated by rotating the point at infinity[0:0:1] in the depth direction. Specific equations are as follows.Vertical Vanishing Point V=[sin Ψ cos φ:−sin Ψ sin φ sin θ+cos Ψ cosθ:sin Ψ sin φ cos θ+cos Ψ sin θ]  (3)Horizontal Vanishing Point H=[cos Ψ cos φ:−cos Ψ sin φ sin θ−sin Ψ cosθ:cos Ψ sin φ cos θ−sin Ψ sin θ]  (4)Normal to screen 10=[−sin φ:−cos φ sin θ:cos φ cos θ]

[x:y:z] indicates a point (x, y, z) in projection geometry. Thecoordinate values of the vertical vanishing point V and the horizontalvanishing point H can be indicated by the equations (1) and (2) bydividing the three-dimensional coordinates of the vertical vanishingpoint V and the horizontal vanishing point H by the Z component.

The horizontal vanishing point can be calculated from the verticalvanishing point V and the horizontal side of the screen 10 according tothe following calculations. The vertical vanishing point V and thehorizontal vanishing point H perpendicularly intersect in athree-dimensional space, as described above. Therefore, when thevertical vanishing point V is indicated by [a:b:c], the horizontalvanishing point H should be positioned on a plane to which the normal isthe vertical vanishing point V. Since the plane to which the normal isthe vertical vanishing point V is expressed by ax+by+cz=0, thehorizontal vanishing point H is positioned on a straight line expressedby ax+by+c=0 by substituting 1 for Z. Therefore, the horizontalvanishing point H is calculated as an intersection of the horizontalside and the straight line expressed by ax+by+c=0.

The vertical vanishing point V can be calculated from the vertical sideand the horizontal side of the screen 10 and the vertical projectionangle theta according to the following calculations. The equation of theleft side or the right side is expressed by Ax+By+C=0, and the equationof the upper side or the lower side is expressed by Dx+Ey+F=0.

Substituting the equations of the vertical vanishing point V and thehorizontal vanishing point H in the equations of the vertical side andthe horizontal side and simplifying the equations yields the followingequations.0=A tan Ψ cos φ+B cos θ+C sin θ+(−B sin θ+C cos θ)tan Ψ sin φ0=D cos φ−(E cos θ+F sin θ)tan Ψ+(−E sin θ+F cos θ)sin φ

Since the vertical projection angle θ can be obtained from the verticalprojection angle determination section 180, unknown numbers included inthese equations are φ and Ψ. Therefore, the vertical vanishing point Vcan be calculated.

The vertical vanishing point V can be calculated from the horizontalvanishing point H and the vertical projection angle θ according to thefollowing calculations. Rotating the equations (3) and (4) with respectto the X axis using the vertical projection angle θ from the verticalprojection angle determination section 180 yields the followingequations:Vertical Vanishing Point V′=[sin Ψ cos φ:cos Ψ:sin Ψ sin φ]Horizontal Vanishing Point H′=[cos Ψ cos φ:−sin Ψ:cos Ψ sin φ]

Since the horizontal vanishing point H′ is known, the component of thehorizontal vanishing point H′ rotated by the vertical projection angle θcan be calculated. In order to calculate the vertical vanishing point V′from the component of the horizontal vanishing point H′, the componentof the vertical vanishing point V′ is multiplied by a constant to yieldthe following equation:Vertical Vanishing Point V′=[cos φ:cos Ψ/sin Ψ:sin φ]=[cos Ψ cos φ:−sinΨ(1/−sin Ψ):cos Ψ sin φ]

Therefore, the vertical vanishing point V′ can be calculated from thehorizontal vanishing point H′ by substituting V′y=H′y−(1/H′y) for the Ycomponent of this equation. After the vertical vanishing point V′ hasbeen calculated, the vertical vanishing point V can be calculated byrotating the vertical vanishing point V′ by −θ around the X axis.

When calculating the vertical vanishing point V from only the verticalprojection angle θ from the vertical projection angle determinationsection 180, the roll angle Ψ is set to be 0 degrees. The verticalvanishing point V equals (0, 1/tan θ) by substituting Ψ=0 in theequation (1) so that the vertical vanishing point V can be calculatedfrom the vertical projection angle θ.

Second Embodiment

FIG. 12 is a functional block diagram of a projector 101 according to asecond embodiment. The projector 101 includes an operation section 160which inputs user operation information 128 instead of the sensingsection 110. The storage section 120 stores operation information 128instead of the sensing information 124.

For example, when the use has performed an operation of moving fourcorners of the projected image 12 toward the four corners of the screen10 using a remote controller, the operation section 160 inputs theoperation information 128 which indicates the operation and stores theoperation information 128 in the storage section 120. The shapedetermination section 130 determines the shape of the screen 10 based onthe operation information 128, and the correction target area settingsection 140 sets the correction target area based on the shape of thescreen 10.

The projector 101 can accurately correct distortion of an image in thesame manner as in the first embodiment without using the sensinginformation, as described above.

OTHER EMBODIMENTS

Application of the invention is not limited to the above embodiments.Various modifications and variations may be made. For example, theinvention may be applied to position detection, image brightnesscorrection, image color correction, and the like in addition to imagedistortion correction.

The condition value in the step S32 is not limited to 10%, and thecondition value in the step S33 is not limited to 3%. An arbitrary valuemay be applied. The conditions in the steps S32 and S33 may be anidentical condition. In the steps S32 to S34, the determination section172 uses the differential value between the aspect ratio of thecorrection target area and the reference aspect ratio. Note that variousvalues (e.g., ratio) which indicate a difference may be employed, forexample.

In the above embodiments, an area is applied which is larger than thescreen 10 by one pixel. Note that the area may coincide with the screen10, or may be larger than the screen 10 by two or more pixels. The areamay be determined based on the ratio of the number of pixels of theliquid crystal panel and the number of pixels of the sensing area.

When the projectors 100 and 101 have a zoom function, the projectors 100and 101 may correct an image depending on the zoom state. Thedifferential image between the sensed images is used in the aboveembodiments. Note that the sensed images 400 and 401 may be directlyused. The calibration image is not limited to the calibration images 300to 302 described above. For example, the projectors 100 and 101 may useonly the calibration image 300 or the calibration image 301, or may usea white and black checkered calibration image instead of the calibrationimage 301.

The projection target is not limited to the screen 10. Variousprojection targets having a rectangular projection target area (e.g.,whiteboard, blackboard, or rectangular frame provided on a wall) may beused. As the projectors 100 and 101, a liquid crystal projector, acathode ray tube (CRT) projector, a projector using a digitalmicromirror device (DMD), or the like may be used. DMD is a trademark ofTexas Instruments, Inc. (U.S.A.).

Although only some embodiments of this invention have been described indetail above, those skilled in the art will readily appreciate that manymodifications are possible in the embodiments without materiallydeparting from the novel teachings and advantages of this invention.Accordingly, all such modifications are intended to be included withinthe scope of the invention.

1. A projector comprising: a projection section which projects acalibration image onto a projection target; a shape determinationsection which determines at least part of a shape of the projectiontarget based on sensing information from a sensing section or operationinformation from an operation section; a correction target area settingsection which sets a correction target area, the correction target areabeing an area along the shape determined by the shape determinationsection; an aspect ratio calculation section which calculates an aspectratio of the correction target area; a determination section whichdetermines whether or not the aspect ratio is appropriate based on afirst criterion when the shape determination section has determined theshape of the entire projection target, and determines whether or not theaspect ratio is appropriate based on a second criterion which isstricter than the first criterion when the shape determination sectionhas not determined the shape of the entire projection target; and animage generation section which generates an image having the shape ofthe correction target area on a projection panel when the aspect ratiois appropriate, and generates an image having a reference aspect ratioon the projection panel when the aspect ratio is inappropriate.
 2. Theprojector as defined in claim 1, wherein the sensing section senses anarea including at least part of the calibration image projected by theprojection section and at least part of the projection target togenerate the sensing information which indicates a sensed image; andwherein the shape determination section determines the shape of at leastpart of the projection target included in the sensed image based on thesensing information.
 3. The projector as defined in claim 1, wherein,when the shape of the entire projection target has not been determinedby the shape determination section, the correction target area settingsection determines coordinate values of a vertical vanishing point and ahorizontal vanishing point formed by sides of the projection target in acoordinate system of the projection panel based on the sensinginformation, and supplements a portion of the projection target whichhas not determined by the shape determination section based on thecoordinate values.
 4. The projector as defined in claim 1, wherein thedetermination section determines whether or not the aspect ratio isadequate by determining whether or not a value which indicates thedifference between the aspect ratio of the correction target area andthe reference aspect ratio is within a predetermined range.
 5. Theprojector as defined in claim 4, wherein, when the shape of the entireprojection target has not been determined by the shape determinationsection, the determination section reduces the predetermined range ascompared with the case where the shape of the entire projection targethas been determined by the shape determination section.
 6. The projectoras defined in claim 1, wherein the correction target area settingsection sets an area larger than the shape determined by the shapedetermination section by at least one pixel as the correction targetarea.
 7. A projected image adjustment method using a projector, themethod comprising causing the projector to: project a calibration imageonto a projection target; determine a shape of at least part of theprojection target based on sensing information from a sensing section oroperation information from an operation section; set a correction targetarea, the correction target area being an area along the determinedshape; calculate an aspect ratio of the correction target area;determine whether or not the aspect ratio is appropriate based on afirst criterion when the shape of the entire projection target has beendetermined, and determine whether or not the aspect ratio is appropriatebased on a second criterion which is stricter than the first criterionwhen the shape of the entire projection target has not been determined;generate an image having the shape of the correction target area on aprojection panel when the set condition is satisfied, and generate animage having a reference aspect ratio on the projection panel when theaspect ratio is inappropriate; and project the image generated on theprojection panel.
 8. The method as defined in claim 7, wherein theprojector senses an area including at least part of the calibrationimage projected by the projection section and at least part of theprojection target to generate sensing information which indicates asensed image, and determines at least part of the shape of theprojection target included in the sensed image based on the sensinginformation.
 9. The method as defined in claim 7, wherein, when theshape of the entire projection target has not been determined, theprojector determines coordinate values of a vertical vanishing point anda horizontal vanishing point formed by sides of the projection target ina coordinate system of the projection panel based on the sensinginformation, and supplements a portion of the projection target whichhas not determined based on the coordinate values.
 10. The method asdefined in claim 7, wherein the projector determines whether or not theaspect ratio is adequate by determining whether or not a value whichindicates the difference between the aspect ratio of the correctiontarget area and the reference aspect ratio is within a predeterminedrange.
 11. The method as defined in claim 10, wherein, when the entireshape of the projection target has not been determined, the projectorreduces the predetermined range as compared with the case where theentire shape of the projection target has been determined.
 12. Themethod as defined in claim 7, wherein the projector sets an area largerthan the determined shape by at least one pixel as the correction targetarea.
 13. A program readable by a computer included in a projectorincluding a projection section, the program causing the computer tofunction as: a projection control section which causes a projectionsection to project a calibration image onto a projection target; a shapedetermination section which determines at least part of a shape of theprojection target based on sensing information from a sensing section oroperation information from an operation section; a correction targetarea setting section which sets a correction target area, the correctiontarget area being an area along the shape determined by the shapedetermination section; an aspect ratio calculation section whichcalculates an aspect ratio of the correction target area; adetermination section which determines whether or not the aspect ratiois appropriate based on a first criterion when the shape determinationsection has determined the shape of the entire projection target, anddetermines whether or not the aspect ratio is appropriate based on asecond criterion which is stricter than the first criterion when theshape determination section has not determined the shape of the entireprojection target; and an image generation section which generates animage having the shape of the correction target area on a projectionpanel when the aspect ratio is appropriate and generates an image havinga reference aspect ratio on the projection panel when the aspect ratiois inappropriate.